Document processors are a class of computer application programs which provide the ability to manipulate, display, and print text and graphics in a variety of formats. One example of a popular document processor program is the Microsoft Word document processor available from Microsoft Corporation. Typically, in most document processors, text may be produced in a variety of fonts, sizes, styles, and paragraph formats. While a number of computer programs provide similar capabilities, document processors provide flexibility and capabilities not found in other programs.
For example, in computer spreadsheet application programs, text information or numerical data is identified with a particular cell which is positioned according to x-y coordinates in the spreadsheet. In this type of system, specific formatting information is associated with individual cells. Thus, the data or text within the cells is easily associated with formatting information based on its relative position in the spreadsheet application. In contrast, in a document processor, text or graphic information may be placed in a document in a position which is dependent primarily on its position within a text string wherein its actual position within a document changes as text or graphic objects are added or deleted from the text string.
Since character positions are variable within a document processed by a document processor, it is extremely difficult to provide fields within such a document. Fields are similar to the formula in cells provided in a spreadsheet application program wherein the contents of a field may be dependent on the mathematical relationship between a plurality of other values.